This application is 371 of PCT/KR99/00036 filed Jan. 22, 1999, which claims the benefits of foreign priority from Republic of Korea Application No. 1998/1797 filed Jan. 22, 1998.
The peptides of the present invention have stronger antimicrobial activities than conventional peptides and have the activity at high salt concentrations.
The present invention relates to biologically active peptides. Every animal on earth possesses biophylaxis systems to defend or protect itself from the infection by virus or bacteria. One of such systems is a non-specific immunity using antimicrobial peptides.
Antimicrobial peptides are considered as a new type of drug due to the following outstanding properties. Firstly, antimicrobial peptides show stronger antimicrobial activities than conventional antibiotics against a broad spectrum of microorganisms. Secondly, antimicrobial peptides have a high industrial applicability which is beneficial to the human body since the antimicrobial peptides show antimicrobial activity against foreign pathogens without destroying the host cells. Thirdly, there is a smaller chance to develop microbial resistance since the antimicrobial peptides show their activity by a mechanism that is totally different from that of the conventional antibiotics, which have serious problems of developing resistance. Studies on antimicrobial peptides began by isolating cecropin from an insect which has an under-developed immune system. After the first finding, magainin, bombinin from amphibians, defensins from mammals were isolated. The studies on antimicrobial peptides are actively performed, and to date, about 2,000 antimicrobial peptides have been identified and reported from species ranging from microorganisms to human.
However, there are several barriers to develop the above mentioned antimicrobial peptides as drugs. Firstly, the conventional antimicrobial peptides act at relatively high concentrations. For instance, in case of magainin, an antimicrobial peptide isolated from epidermis of an amphibian, the active concentration is 50-200 xcexcg/ml (Zasloff M. (1987) Proc. Natl. Acad. Sci. USA, 84: 5449-5453) even though it is effective against Gram-positive and Gram-negative bacteria and fungi. This concentration range is quite high considering that the conventional antibiotics act against a specific microorganism in the range 0.1-1 xcexcg/ml. Secondly, the antimicrobial activity of the antimicrobial peptides is sensitive to salt concentration. In case of cystic fibrosis that invades the human lung, for instance, the antimicrobial peptide was not effective due to an abnormal increase of the salt concentrations at the site of invasion (Goldman, M. J. et al. (1997) Cell, 88: 553-560).
Antimicrobial peptides isolated from Korean toad were reported by the present inventors in Biochemical and Biophysical Research Communications 218, 408-413 (1996). These antimicrobial peptides known as buforin I and buforin II showed strong antimicrobial activities against a broad-spectrum of microorganisms including Gram-positive and Gram-negative bacteria and fungi. Buforin I and buforin II also have antimicrobial activities at a concentration of 1-4 xcexcg/ml, which is stronger than that of conventional antimicrobial peptides.
These antimicrobial peptides, however, are also sensitive to salt concentrations. Therefore, it has been desired to develop antimicrobial peptides that have an enhanced antimicrobial activities and are not sensitive to salt concentrations to have antimicrobial activities in vivo.
It is an object of the present invention to provide novel biologically active peptides.
Another object of the present invention is to provide peptides that have antimicrobial activities against a wide variety of microorganisms with stronger antimicrobial activities.
It is another object of the present invention to provide peptides that are insensitive to salt concentrations in potentiating the antimicrobial activity.
A further object of the present invention is to provide a secondary structure of peptides that are not sensitive to salt concentration in potentiating the antimicrobial activity.
Another object of the present invention is to provide a precursor peptide that could prepare biologically active peptides.
Still another object of the present invention is to provide cDNA that can code for biologically active peptides.